Tone arm for phonographs



Margh 1 1927' M. M. GRUBER. 6 9 6 TONE ARM FOR PHONOGRAPHS' Filed July '12, 1q23 I INVENTOR BYW a. g f /l TTORNE Y5 Patented Mar. 1, 1927.

MORRIS M. GRUBER, or EAST ORANGE, NEW JERSEY, Assrsnon, :BYirnsNE Assiem 1,519,467 PATENT OFFICE.

MENTS, TO SONORA PHONOGRAPH COMPANY, INC., OF NEW YORK, N. Y., :A' COB- PORATION OF NEW YORK.

TONE ARM FOR PHONOGRAPI-IS.

Application filed July 12,

This invention relates to tone arms for phonographs. These arms usually comprise two parts, one part mounted in the motorboard of the machine for pivotal movement about a vertical axis, and the other part which carries the sound box pivotally connected to said first part for moving about a horizontal axis. In certain types of phonographs, it has been the practice to prov de the first of said parts, that-is, the part p1voted for movement about a vertical axis, with a cylindrical bearing at its end into which is fitted a similarly-shaped journal carrying the first of said parts. Said hearing and journal portions were of comparatively large diameters. that is, an inch or more, so that the cylindrical bearing surface was comparatively large. This resulted in difficulty in obtaining aclose fit between these parts, for as is well known, it is much more difiicult to fit a journal in a bearing of large diameter than in one of small diameter, and, in addition, the large-surface bearings wear much more rapidly. The result of these imperfect fittings was a-=rattl1ng between the parts, which caused an imperfection in the nature of a chattering sound, in the playing of a record. It is one of the objects of my present invention to overcome the disadvantages hereinbefore specified and others, and to provide a novel swivel conmotion between the parts of the tone arm, whereby any possibility of chattering is eliminated.

It is a further object of my invention to provide in the swivel joint a bearing of a relatively small diameter. thus making it possible to obtain exact fittings between the journal and the shaft of said joint.

It is a further object of my invention to provide a construction similar to that previously used in the respect that a cylindrical portion of large diameter is formed on the end of the part of the tone arm which is vertically pivoted, and in said cylindrical portion is fitted a cooperating cylinder which carriesthe other part of the tone arm but without possibility of any defect in transmission of sound being caused by im perfection of fit between said cylindrical portions.

It is a further object of my invention to provide a swivel joint between the parts of the phonograph tone arm which will not be- 1923. Serial No. 650,992.

rendered defective by wear of the even after a long period of use.

Other objects and advantages will appear parts,

as the nature of the improvements is better understood, the invention consisting sub stantially in the novel arrangement and corelatlon of instrumentalities herein fully described, and illustrated in the accompanying drawings, wherem similar reference charac ters are used to describe corresponding parts throughout the several views, and then finally pointed out and specifically defined and indicated in the appended claims.

The disclosure made'the basis of exemplitherefore, is to be understood from an illustrative, rather than a restrictive, standpoint.

The inventive idea involved is capable of receiving a variety of mechanical expressions, one of which, for the purposes of illustration, is shown in the accompanying drawings, in which- Fig. 1 is a front view of a phonograph tone arm having my invention applied thereto.

Fig. 2 is a shown in Fig. 1.

Fig. 3 is a disassembled view of the tone arm shown in Figs. 1 and 2, parts being broken away to structure.

Fig. 4: is a section taken on the line 44 of Fig. 2. I

Fig. 5 is a vertical section taken substantially on the line 5-5 of Fig. 2.

Referring to the drawings, there is shown a phonograph horn which may be of any ordinary type but more particularly that employed in the machines of the concealed horn type, and consists of twoparts 10, and 11, part.10 being rotatably mounted in a collar 12 which is secured to the motor-board 13 in any suitable manner, as by screws 14, and the part 11 being swiveled to the part 10 and adapted to carry at its forward end 16 the reproducer or sound box (not shown). The part 10 may be referred to in this specification as the amplifying portion of the arm, while the part 11 may be referred to as the reproducer part. The'part 10 is, therefore, rotatable about a vertical axis,

plan view of the tone arm illustrate the underlying which maybe indicated at A-A, so that the tone arm may travel in a horizontal plane.

The part 11 is swiveled to the part .10 for V rotation about a.horizontal axis, which may to the part 10 by a swivel ioint, the part;10

is provided at its forward end with a cylindrical pportion 15,.thea axis of which is horizontal. Within saidcylindrical portion is adapted to fit a barrel 18. (The cylinder 15 is provided withv acut-out portion extending substantially half way around its circumference inwhich space the portion 11 is adapted to'operate. Said portion is proyvidedwvith acylindrical"rearward end 21 adapted ztO fit :into the barrel 18 by way of cut-outportion 23, which is of a size sufficient toiaccommodate cylindrical portion 21 snugly. ,The cut-out portion 23 is smaller than cut-out portionQO, so as to permit IIIIOVEIIIQIlt015411711121 and barrel 18 to-which it is connected about. a horizontal axiswithin of' sound waves therethrough into the amplifying portion 10.

drical portion 15 whichacted as a bearing. The portion 15 was usually. an inch or more in diameter, and its length also in excess of one inch.

mwhich :destroyedfthe effect of the record which was being played at the time. By

.-my invention. I eliminate the large-diameter,

large-surface bearing 15, and provide a very small-diameter, small-surface hearing which is easily manufactured and which. even after long use, Jdevelops very little,. if any, lost imotion orfree :play. For this purpose I provide a shaft .25 supported in end: mem- 1bers26, 27.each of said BIlCl'IDGHlbQISdlEIV- sing a shoulder 28, 29-respectively adapted to seat against the peripheries 30, 31 respectively at the ends of the cylindrical portion 15. 'Saidshaft 25 may he in the form of a bolt extending through the end members 26, 27, said bolt being: provided with a head32 atone end and having a threaded portion 33 atiits other end on which is adapted to screw a nut I34, which enters a depression 35, formed in the endhmemberfl'i. so that said nut is countersunk. "By drawingup-the bolt tightly against the two end members 261and In order to make -an accurate bearing, careful machmmg was necessary 27, said end members are brought :into firm engagement with the edges 30, 31 of the cylindrical portion 15, so that no movement can take place between said end members and said cylindrical portion. The shaft25 is thus 'Ltirmly and rigidlyfixed inposition relative to cylindrical portion 15 and amplitying portion 10 of the tone arm. Upon this rigid shaft 25, I rotatably mount the barrel 18. For this purpose I provide said barrel with inset heads 10, 11 at the center of which Ifoi'm hubs 42, 43, the opening through said hubs being ground to a size just suiticientuto permit thebarrel 18-wto be rotated freely on shaft 25 without appreciablerfree play or lost motion. It is thus apparent that the only contact of thebarrel 18 with its supporting shaft is by the small-diameter,

small-surface hubs 12, 13. The contacting surfaces between the hubs lor'bearings land the shaft journalled therein are soismall that accuracy in fitting is 'easily obtainechand-the wear upon said contacting surfaces isnegligible, evenafter along period of use. "It is.therefore.apparent that it is now 110 longer necessary tocfit the "barrel 18 accucylindrical portion 15. The barrel 18 is, of course, hollow, to permit the: transmission rately within cylindricalzpontion 15. because the movement of said barrel: relativeitocy .lindrical portion 15 is determined by the bearingseLQ, 43 and shaft 25,-rather than by V In previous constructions, thebarrel 18 was ground itoa snug fit within the cylinthe large-diameter, large-surface -bearings between the circumference of portion 18 and the innersurface of cylindrical portion-1 5; So that, if there. is anaccuratefit of shaft 25' inthe small bearings 42, 43,-which=%is easily obtainable," there will henna-rattling of the barrel 18 withincylindrical portion 15. even ifthere .-is a great deal of space between said barreland said portion.

Within one of the depressions formed by the wall of the cylinder and the inset heads 40 and 41 (here shownas the-depression formed by the head 41) is positioned a leaf springb-O carrying at oneaendaa detent 51, extending through the wall of thebarrel 18, andadapted to contact with grooves 52 and 53 for maintaining the reproducer portion11 in raised or lowered position.

' In accordance with the provision's of-the patent statutes,.I have described the prin ciple of my invention together with the ap paratus which I now consider to represent apractical embodiment thereof, but'I desire it understood that my invention is not confined to the particular form ofapparatus herein shown and vdescribedithe same being merely illustrative, andjthat the invention can be carried out in-other Ways without d-epartingfrom the spirit of *my invention, and, therefore, I claim broadly the right to employ all equivalent instrumentalities coming within the scopeofilthe appended claims, and by meansof which the objects ofmy invention are-attained and the new results accomplished, as hereln set forth, as it isobvious that the particular embodiments herein shown and described are only some of many that can be employed to attain these objects and accomplish these results.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. A device 'of the. character described comprising a tone arm having a reproducing section and an amplifying section, a joint connecting said sections comprising a hollow cylinder carried by one of said sectionsand a second hollow cylinder carriedby the other of said sections and adapted to'fit concen trically Within said first cylinder, said second cylinder having inset heads each pro vided with a central hub, end plates for said first cylinder each provided with a central perforation and a shaft adapted to pass through said hubs and said perforations and to form an axle to rotatably support the second cylinder in spaced relation to said first cylinder and aleaf spring positioned upon the inner wall of said second cylinder against one of said heads, said spring having a detent projecting through the wall of said cylinder and adapted to engage grooves in the wall of said first cylinder, whereby said reproducer portion of said tone arm may be locked in raised or lowered position.

2. In a device of the character described a tone-arm having a reproducer section and an amplifying section, a joint connecting concentric with the first cylinder and being provided with inset heads carryin hollow hubs, a shaft extending through sa1d plates and rotatably mounted in said hubs, means carried by said shaft and engaging said plates to hold said shaft against movement relative to said plates and a leaf spring positioned upon the wall of said second cylinder against one of said heads, said spring having a detent projecting through the wall of said cylinder and adapted to engage grooves in the wall of said first cylinder whereby said reproducer portion of said tone arm may be locked by said detent in raised or lowered position. v

This specification signed this 15th day of June, 1923.

MORRIS M. GRUBER. 

